1. Field of the Invention
The present invention relates generally to utilizing drilling fluid in well cementing operations, and more particularly, to methods of cementing a well with a cementing composition which includes a portion of the drilling fluid used to drill the well.
2. Description of the Prior Art
A variety of drilling fluids are used in drilling well bores. Generally, the drilling fluids are solids containing water based gels or hydrocarbon based fluids which can be non-weighted or weighted with particulate weighting material such as barite. After a well bore is drilled during which the drilling fluid used is circulated through the well bore, the circulation of the drilling fluid is stopped while the well is logged and a string of pipe is run in the well bore. After the pipe is run, the drilling fluid in the well bore is cleaned up by circulating drilling fluid downwardly through the interior of the pipe and upwardly through the annulus between the exterior of the pipe and the walls of the well bore while removing drilling solids and gas therefrom. Primary cementing operations are then performed in the well bore, i.e., the string of pipe disposed in the well bore is cemented therein by placing a cementing composition in the annulus between the pipe and the walls of the well bore. The cementing composition sets into a hard substantially impermeable mass whereby the pipe is bonded to the walls of the well bore and the annulus is sealed. When the cementing composition is run down the pipe and into the annulus, the drilling fluid in the pipe and annulus is displaced therefrom. The used drilling fluid is generally accumulated in a pit or tank and then disposed of.
The disposal of drilling fluid is time consuming and expensive, particularly in offshore drilling locations, in that drilling fluid often must be disposed of as a fluid which is hazardous to the environment. Thus, any environmentally safe use to which all or part of the drilling fluid could be put at a well site thereby eliminating the need for disposing of the drilling fluid would be highly advantageous.
By the present invention, methods of cementing wells with cementing compositions containing drilling fluid are provided. That is, a portion of the drilling fluid used to drill a well is utilized as a component in the cementing composition used for cementing the well. The portion of the drilling fluid which is not utilized in the cementing composition can be disposed of conventionally, or it can ultimately be formed into a hard environmentally safe cementitious mass in an underground or other location.